Hello,
1.7 is equal to 17 tenths. (just move the decimal to the right by 1 value).
0.8 is equal to 8 tenths.
17 tenths - 8 tenths = 9 tenths
9 tenths = 0.9 (move the decimal to the left by 1 value)
The answers are 17, 8, 9, and 0.9, respectively.
Hope this helps!